Yukon 8.6in GM 4.56 Rear Ring & Pinion Install Kit 30 Spline Positraction Axle Bearings and...

A 1999-2008 Silverado, Sierra, Tahoe or Suburban half-ton on 35 inch tires with the factory 3.42 or 3.73 gears feels like it is towing a trailer even when it is not, and a worn or broken factory locker leaves you with one tire spinning in the mud. The Yukon Gear and Axle YGK2019 fixes both in a single box for the GM 8.6 inch 10-bolt rear: a 4.56 ring and pinion set, a 30-spline Yukon Dura Grip clutch-type limited slip, the Yukon master install kit with Timken bearings, and new axle bearings and seals. It is everything that goes inside the housing for a full regear and traction upgrade.

What this package does in a GM 8.6 rear

The 8.6 is GM's C-clip 10-bolt used under its half-ton trucks and SUVs with rear disc brakes, with a 10-bolt cover and 10 ring gear bolts. The 4.56 ring and pinion lowers the final drive so the engine stays in its torque band with a much taller tire. The Dura Grip replaces your factory carrier with a clutch-style limited slip that sends torque to the tire with grip rather than letting the free tire spin. Yukon notes its positraction units are fully rebuildable, so the clutch packs can be serviced later instead of replacing the whole carrier.

The master install kit supplies the Timken pinion and carrier bearings and races, pinion seal, shims, crush sleeve, pinion nut, ring gear bolts and the setup consumables. The carrier bearings in this package have a 3.062 inch outside diameter, which matches the 1999-2008 8.6. Because the axle shafts have to come out to change the carrier anyway, Yukon adds the wheel bearings and axle seals so the whole axle is fresh when the cover goes back on.

Signs a 1999-2008 GM 8.6 needs this work

• Lazy acceleration, constant downshifting and poor fuel economy after a big tire upgrade
• Whine that changes between throttle and coast from worn gears or loose pinion bearings
• One wheel spinning on wet grass, snow or mud because the open carrier or factory locker is no longer working
• Clunk on and off the throttle from a loose pinion or worn carrier
• Leaking axle seals and rumble from the wheel bearings at the ends of the housing

How to confirm the axle before you buy

Count the cover bolts: the 8.6 has a 10-bolt cover. Check for rear disc brakes, which separate the 8.6 from the drum-brake 8.5. Find the RPO axle code on the glovebox label to confirm your factory ratio and whether the truck has a factory locker. Then count the axle spline: this package is 30-spline. If your gears and carrier are fine and you only have bearing noise, the Yukon YK GM8.6-A master overhaul kit is the cheaper fix.

Fitment

This package is for the GM 8.6 inch rear with 30-spline axles in 1999-2008 trucks and SUVs, with a 10-bolt cover, 10-bolt ring gear and carrier bearings of 3.062 inch outside diameter. GM changed the 8.6 pinion bearings for 2009, so a 2009-and-newer truck needs different parts. Confirm the RPO code and the year, or send us your VIN and we will check it. More differential parts are under rebuild kits.

Install notes

• Pull the C-clips and axle shafts, remove the carrier and pinion, and drive out all the old races. Pinion depth, pinion bearing preload, carrier preload and backlash all have to be set to Yukon's specs before you read the contact pattern.
• Hold the yoke with a pinion flange holding tool while crushing the sleeve, and creep up on preload in small steps. Overshoot means a new crush sleeve.
• A dial indicator with magnetic base is needed for backlash and ring gear runout.
• Fill with 75W-90 gear oil, and add limited-slip additive if the Dura Grip instructions call for it.
• Break the new gears in gently, avoid towing during break-in, then change the oil. Update the axle ratio in the truck's computer so the speedometer and shift points match.
• A nodular iron 8.6 cover protects the new gears on trail trucks.

Does this fit my 2010 Silverado 1500?

No. This package is built for the 1999-2008 8.6. GM changed the pinion bearings in 2009, so 2009-and-newer trucks need different install parts.

My truck has the factory locker. Can I keep it?

This package includes a new Yukon Dura Grip limited slip, which replaces the factory carrier. If you want to keep your locker, buy the gear set and install kit separately and check that your carrier accepts 4.56 gears.

Are axle bearings and seals included?

Yes. YGK2019 adds the wheel bearings and axle seals on top of the gears, carrier and master install kit.

What fluid does the rear take after the regear?

75W-90 gear oil. Follow the Dura Grip instructions on whether limited-slip additive is needed.

Is 4.56 the right ratio for my tires?

4.56 is a common pick for half-tons on roughly 35 inch tires. If you run smaller tires or mostly highway miles, a 4.10 or 3.73 may suit you better. On a 4x4, the front gears must match.